.gamma.-Fe.sub.2 O.sub.3, Fe.sub.3 O.sub.4, their intermediate oxides (such iron oxide type ferromagnetic particles are referred to as "FeO.sub.x (4/3.ltoreq.x.ltoreq.3/2)" herein), Co-containing chromium dioxide and ferromagnetic alloy particles have been mainly used as ferromagnetic particles for magnetic recording media.
Recently, iron nitride type magnetic layer has been studied and suggested for use as a magnetic layer of a magnetic recording medium. Examples thereof include .alpha."-Fe.sub.16 N.sub.2, .gamma.'-Fe.sub.4 N (referred to as "Fe.sub.4 N" hereinafter), .epsilon.-Fe.sub.x N (2&lt;x.ltoreq.3) (referred to as "Fe.sub.2-3 N" hereinafter) and Fe.sub.4 N is very suitable in terms of initial magnetic properties as a magnetic material for a magnetic recording medium. Many approaches have been made to use such iron nitride in a magnetic recording medium. However, its weather resistance is poor and its magnetic characteristics greatly deteriorate with the passage of time, and thus it has been difficult to put it into practical use.
In order to avoid the above defects, it has been suggested in Japanese patent application (OPI) No. 76105/85 (the term "OPI" used herein means a published unexamined patent application) that surfaces of iron nitride particles be coated with oxides such as iron oxide. Further, it is also suggested in Japanese patent application (OPI) No. 59304/82 that iron nitride (Fe.sub.4 N) be used in an amount of from 10 to 70% based on iron metal particles mainly comprised of iron in a magnetic recording medium.
However, even though surfaces of iron nitride particles are simply coated with oxides in accordance with the above, the dispersibility of the particles is insufficient, and C/N and weather resistance of the thus obtained magnetic recording medium are also insufficient.